Reducing total phosphorus levels in wastewater to phosphorus concentration levels of about 0.5 mg/L or less when using a biological secondary treatment stage often requires use of a tertiary treatment stage after the biological treatment stage. Such tertiary stages may use a chemical treatment system to remove the phosphorus from the biologically treated water. The chemical treatment system may include adding metal salts, such as aluminum and iron salts, to precipitate or otherwise insolubilize the phosphorus, and then separating the precipitated and other insolubilizied phosphorus from the chemically treated water or wastewater. Although such chemical treatment systems can reduce the total phosphorus concentrations to levels of 0.5 mg/L or less, the operating and other costs for these systems, including the cost of the chemical, space for storing the chemical, the disposal costs for the solids formed by the chemical treatment and so on, are often high, making these chemical treatment systems relatively expensive to operate. Similar issues for attaining very low phosphorus levels in other types of water may arise when using a biological treatment as part of the water treatment process.
Accordingly, improved water and wastewater treatment systems are needed in the art.